This invention relates to systems which can be used to open a tow of fibers such that the resulting xe2x80x9copened towxe2x80x9d of fibers has a shape useful in the production of absorbent structures, and more particularly to an air opening jet apparatus and method for use in such systems and products formed by such systems.
Many types of filaments, fibers and yarn (collectively xe2x80x9cfibersxe2x80x9d) are sold as a xe2x80x9ctowxe2x80x9d in which a plurality of such fibers are compressed together, optionally with crimping, by methods known to those skilled in the art in order to maximize the content of the packing systems, for example, bales, by which such tows are sold and delivered to users of tow. Before use, such users generally xe2x80x9copenxe2x80x9d such tow, separating the compressed fibers by a distance greater than that in the compressed state. Numerous methods and devices for opening tows are known and described in the art. Examples include U.S. Pat. Nos. 3,282,768, 3,523,059, 3,099,594, 4,522,616, 2,794,480, 3,032,829, 5,591,297 and 5,203,757 whose teachings are incorporated herein by reference. While such devices have found utility in various applications, such devices typically produce xe2x80x9copenedxe2x80x9d tows which were substantially circular in cross-section, for example, tows used to make smoke filters or writing instrument reservoirs. However, for other applications a rectangular shape is preferred; for example, absorbent structures which are intended for use in personal care products such as diapers, bandages, hygiene pads and similar absorbent products. For such uses a shape that has a substantially rectangular cross-section is preferred. A representative sampling of these various types of products are disclosed in U.S. Pat. Nos. 4,289,130, 5,171,235, and 5,928,452, U.S. Statutory Invention Registration No. H1565, and PCT International Publication No. WO 99/30661.
It is also known to use, in systems of the foregoing types, air jets which open the tow and form it into a rectangular shape for use in tobacco filter rods and the like, as disclosed in U.S. Pat. Nos. 4,468,845 and 4,435,239. One of the significant advantages asserted for these systems is the fact that the air opening jet employed in the system is designed to operate at very low air pressures (e.g. less than 3 psi), which is said to eliminate the need for the large capital investment in expensive air compressing and piping facilities normally associated with air opening or xe2x80x9cbloomingxe2x80x9d systems. This low pressure air is utilized to move the tow through the air opening jet, during which the tow is opened, and then through a bustle assembly in which the opened tow is decelerated and retarded in the bustle assembly to obtain the desired opening and density of the tow. This deceleration and retarding of the tow is obtained by an adjustable tension arrangement for engaging the tow, and more particularly by a flat, imperforate xe2x80x9ctensionxe2x80x9d plate that is pivotally mounted at one of its ends within the bustle assembly, and a relatively complex mechanical arrangement for adjusting the movement of the pivoted tension plate toward and away from the tow to thereby vary the tension force applied to the tow by the tension plate.
In accordance with one aspect of the present invention, an air opening jet apparatus is provided for use in a system for opening a thin, relatively wide tow of textile filaments held together by crimping and forming the opened tow into a predetermined shape suitable for use, for example, as an absorbent structure for personal care products. The air opening jet apparatus includes a housing having an inlet opening for receiving a partially opened tow and having a configuration corresponding generally to the shape of the partially opened tow. The housing also has an outlet opening through which the tow exits the housing and this outlet opening has a configuration corresponding generally to the predetermined shape.
An air jet is formed within the housing adjacent the inlet opening thereof to create a venturi which moves the tow through the air opening jet apparatus and which also further opens the tow, and a source of compressed air communicates with the air jet to provide carrier air for moving the tow through the air opening jet apparatus.
A forming chamber is provided within the housing and downstream of the air jet that includes a gradually increasing cross-sectional area in the direction of flow of the tow that corresponds to the predetermined shape, the air jet being disposed within the housing to cause the tow to be fully opened and to substantially fill the forming chamber as it moves therethrough.
An accumulating chamber is located within the housing downstream of the forming chamber that is constructed and arranged to permit the opened tow to accumulate within the accumulating chamber and be withdrawn from the housing at different flow rates through the housing outlet opening in the predetermined shape. The accumulating chamber includes at least one perforated plate disposed in the path of the tow and the carrier air moving therethrough to cause the tow to engage the perforated plate and to cause at least some of the carrier air to pass through the perforated plate.
A control valve is provided for maintaining the flow of the carrier air at a level that will cause at least the portion of the carrier air to pass through the perforated plate and urge the tow into frictional engagement with the perforated plate with sufficient force to retard the movement of the tow through the accumulating chamber and cause the tow to accumulate in the accumulating chamber.
In the preferred embodiment of the present invention, the accumulating chamber may include a second perforated plate located in spaced relation to the first above mentioned perforated plate, and the tow moves between the perforated plates and is urged into engagement therewith by the carrier air passing through both the perforated plates. Finally, in the preferred embodiment of the present invention, the predetermined shape of the outlet opening in the housing is rectangular.
Another aspect of the present invention provides an apparatus and method by which one or more air opening jets of the aforesaid type may be utilized for opening and forming multiple tows into a composite multi-tow band of a predetermined shape suitable for use, for example, as an absorbent structure for personal care products. In this type of system, instead of a single tow being delivered to the inlet end of an air opening jet apparatus, two separate and distinct tows are delivered to the inlet end of a single air opening jet or to separate air opening jets and are combined therein or downstream therefrom into a composite multi-tow band.
In this system, a first arrangement is provided for receiving a first tow from a tow bale having a predetermined denier units per filament, spreading the filaments in the first tow into a first tow band, and having an exit end for discharging the first tow band therefrom with a predetermined width. A second arrangement is provided for receiving a second tow from a second tow bale having a predetermined denier units per filament which is different from the predetermined denier of the first tow, spreading the filaments in the second tow into a second tow band, and having an exit end for discharging the second tow band therefrom with a predetermined width. The first and second tow bands are then simultaneously introduced into the inlet end of the air opening jet apparatus and moved therethrough for opening and forming as described above in connection with a single tow. The first and second tow bands can also be introduced to two separate air opening jet apparatuses.
Each of said first and second arrangements may preferably comprise a tow banding jet for receiving the respective first or second tow and spreading the tow into the form of a band, and at least one pair, and preferably multiple pairs, of delivery rolls disposed between the first and second banding jets, respectively, and the air opening jet apparatus or apparatuses.
In one contemplated embodiment of this system, the width of the exit end of one of the first or second banding arrangements is smaller than the other, whereby the multi-tow band discharged from the exit end of the air jet opening apparatus or apparatuses has one tow band that is larger in width than the other. It is preferred that the tow band having the larger width have a denier per filament that is less than the denier per filament of the other tow band. Additionally, the system may include a surfactant applicator located upstream of the inlet of the air opening jet for applying a surfactant to the tow band having a smaller width, and the system may include a bonding agent applicator located upstream of the inlet of the air opening jet for applying a bonding agent to the tow band having a larger width. It is also possible to individually vary the delivery speed of the two tow bands to the inlet of the air opening jet apparatus, and to individually control the bloom of the two tow bands.